1. Field of the Invention
This invention relates to a method and an apparatus for removing clogging material from clogged granular filter medium of a granular filter device. More specifically, this invention relates to a method and an apparatus for removing the clogging material from the granular filter medium of a final granular water filter utilized in water purification.
2. Information Disclosure Statement
The present invention is applicable to water treatment filter devices of the type which utilize a granular filtering medium. Examples of granular filtering mediums include anthracite, activated charcoal, pumice stone, expanded clay, sand, gravel, etc., including multi-medium combinations thereof. Present granular filters utilize a periodic backwash process to remove particulate material clogging the granular filtering medium. The backwash process requires a major flow of a backwash fluid in a direction reverse that of the normal filtering operation. Generally, the backwash flow passes upwardly through the granular filter medium. Whereas the raw fluid which is to be filtered is introduced into the upper portion of a tank which contains the filtering medium and flows downwardly through the granular filtering medium wherein the entrained liquid and/or solid impurities are removed by the action of the filtering medium.
During the backwash process a substantial portion of the granular filter medium is entrained within the backwash flow along with the loosened clogging material. In order to retain the entrained filter medium, the level of the outflow channel is positioned at a point where the least amount of entrained filter medium is lost and the greatest amount of loosened clogging material is removed for a given rate of flow of the backwash. The problem with this type of backwash process is that when the process terminates, the clogging material which was not discarded with the backwash fluid falls back onto the granular filter medium.
The present invention overcomes the aforementioned inadequacies of the prior art by the provision of a collector disposed within the granular filter device for collecting the clogged granular filter medium and a portion of the water from the tank housing the clogged granular filter medium and water and pumping the clogged granular filter medium and water such that an aqueous slurry is formed and flows from the filter device to a reservoir thereby causing the clogged granular filter medium to be agitated resulting in an intergranular frictional action of the clogged granular filter medium such that the clogging material is loosened from the granular filter medium such that a suspension of loosened clogging material and entrained granular filter medium is formed. When the suspension of loosened clogging material and entrained granular filter medium enters the reservoir, the entrained granular filter medium settles to the bottom of the reservoir. The settled granular filter medium is conveyed by a separator for separating the granular filter medium from the suspension of clogging material. A means for transporting the granular filter medium to the tank housing the granular filter medium repositions the cleaned granular filter medium in the tank of the granular filter device.
It is an object of the present invention to provide a method to clean and remove clogging material from an aqueous slurry of clogged granular filter medium of a granular filter device such that the cleaned granular filter medium may be reused in the granular filter device.
Another object of the present invention is to provide a method with an apparatus to clean and to remove clogging material from the granular filter medium used in a granular filter device by agitating the clogged granules forming the granular filter medium.
Another object of the present invention is to provide a method with an apparatus to clean and to remove the clogging material lodged in the pores or voids between granules forming the granular filter medium.
Another object of the present invention is to provide a method of removing impurities or clogging material attached to the granular filter medium from the granular filter medium positioned in the interior of the tank containing the granular filter medium without the expenditure of large amounts of time or backwash liquid.
Another object of the present invention is to provide a method with an apparatus to clean and to remove clogging material such as particulate matter from the granular filter medium used in a granular filter device to purify raw water.
Another object of the present invention is to provide a method and apparatus to clean and to remove clogging material from the granular filter medium used in a granular filter device in order to prolong the use of the granular filter medium.
Another object of the present invention is to provide a method and apparatus to clean and to remove clogging material fromthe granular filter medium used in a granular filter device where the filter device includes a pressure granular filter or an open gravity granular filter.
Another object of the present invention is to provide a method with an apparatus which agitates the clogged granular filter medium thereby resulting in an intergranular frictional action of the clogged granular filter medium to thereby loosen the clogging material from the granular filter medium used in a granular filter device.
Another object of the present invention is to provide a method with an apparatus to clean and remove the clogging material from the granular filter medium of a granular filter device which remains notwithstanding a backwash of the filter.
In the past, when particulate matter or the like has accumulated in the pores or voids between the granular filter medium of a granular filtering device, the particulate matter positioned between the granular filter medium was only partially removed by backwashing the granular filter medium.
A need has existed in the art for a method for removing such build-up of particulate matter in the voids within the granular filter medium other than backwashing the clogged granular filter medium.
The present invention provides a method and an apparatus which may be completely self contained, mobile and which enables an operating crew to remove the clogging particulate material from the clogged granular filter medium of a granular filer device while preventing the loosened clogging material from repositioning itself at the top of the filter at the end of the cleaning process.
The granular material can be sand, stone, anthracite, and the like which is positioned within a filter device. Such granular filter devices are used in water purification (tertiary treatment) and in waste water treatment. In water purification the granular filter medium is present in the final filter and may be sand to remove the turbidity or charcoal to remove color and/or taste impurities.